Test tube



FIG. 1 is a front elevational view of a test tube, showing our new design, with all other sides being identical thereto;

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a top plan view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a test tube, as shown and described. 